You have to turn the bar into a pivot point for the elbows, and for that to happen, it needs to be in the right place. When turning over the bar, pull the elbows high and to the sides to bring the bar to the upper chest. As you begin to turn the elbows over, retract the shoulder blades and pull the elbows back before they come around - in other words, pull the bar up and back into the throat. Then the elbows can spin around it without much resistance and with the bar staying in immediate proximity to the body so it's delivered smoothly to the shoulders.